Delete expired keys on the "Get" request.

[sitaram-kalluri]

Is your feature request related to a problem? Please describe.

Currently, on a "get" request to a key, if the key is expired, "data: null" is returned, but the key remains in the Key-Store until a batch process (that removes expired keys) runs.

Describe the solution you'd like

Additional to the above behaviour, On Get request, if a key is found to be expired, delete the key and then return "data: null"